Add documentation on the BoringSSL test suite integration

                   Enable building of integration with external test suites.

                   This is a developer option and may not work on all platforms.

                   The only supported external test suite at the current time is

                   the BoringSSL test suite.

                   the BoringSSL test suite. See the file test/README.external

                   for further details.

  no-filenames

                   Don't compile in filename and line number information (e.g.

Running the BoringSSL test suite with OpenSSL

=============================================

It is possible to integrate external test suites into OpenSSL's "make test". At

the current time the only supported external suite is the one used by

BoringSSL.

This capability is considered a developer option and may not work on all

platforms.

In order to run the BoringSSL tests with OpenSSL, first checkout the BoringSSL

source code into an appropriate directory:

$ git clone boringssl https://boringssl.googlesource.com/boringssl

The BoringSSL tests are only confirmed to work at a specific commit in the

BoringSSL repository. Later commits may or may not pass the test suite:

$ cd boringssl

$ git checkout 490469f850e

From the OpenSSL source code configure to use the external tests:

$ cd ../openssl

$ ./config enable-ssl3 enable-ssl3-method enable-weak-ssl-ciphers \

  enable-external-tests

Note that using other config option than those given above may cause the tests

to fail.

Run the OpenSSL tests by providing the path to the BoringSSL test runner in the

BORING_RUNNER_DIR environment variable:

$ BORING_RUNNER_DIR=/path/to/boringssl/ssl/test/runner make test

Note that the test suite may change directory while running so the path provided

should be absolute and not relative to the current working directory.

To see more detailed output you can run just the BoringSSL tests with the

verbose option:

$ VERBOSE=1 BORING_RUNNER_DIR=/path/to/boringssl/ssl/test/runner make \

  TESTS="test_external" test

Test failures and suppressions

==============================

A large number of the BoringSSL tests are known to fail. A test could fail

because of many possible reasons. For example:

- A bug in OpenSSL

- Different interpretations of standards

- Assumptions about the way BoringSSL works that do not apply to OpenSSL

- The test uses APIs added to BoringSSL that are not present in OpenSSL

- etc

In order to provide a "clean" baseline run with all the tests passing a config

file has been provided that suppresses the running of tests that are known to

fail. These suppressions are held in the file "test/ossl_shim/ossl_config.json"

within the OpenSSL source code.

The community is encouraged to contribute patches which reduce the number of

suppressions that are currently present.